Base Plate

• The disk or flat surface on which the rest of the compass is situated is called the base plate. It is flat and usually transparent so that it can be placed on top of a map. Often, base plates include a magnifier to study map details. Other features that the base plate can offer to help orient a compass with a map include a direction-of-travel arrow, a scale and a ruler.
  
  

Compass Needle

• A very thin piece of metal, the needle sits on a tiny point so that it can smoothly rotate. The half of the needle that is painted red is magnetized and will point north; the other half is usually left unpainted, or painted black or white.
  
  

Compass Housing

• The compass housing is the sealed plastic compartment that encases the needle. It's often filled with liquid to keep the needle from swinging back and forth too loosely, and includes a bubble so that users know that the compass is level.
  
  

Dial

• The dial is the labelled ring around the compass housing. This area is often marked with degrees and directions, and can be rotated so as to align with the needle.